title: Targeted deletion of GSNOR in hepatocytes of mice causes nitrosative inactivation of O6-alkylguanine-DNA alkyltransferase and increased sensitivity to genotoxic diethylnitrosamine.
abstract: S-nitrosoglutathione reductase (GSNOR), a ubiquitously expressed protein central to the control of protein S-nitrosylation, plays critical roles in many biological systems. We showed recently that GSNOR is often deficient in human hepatocellular carcinoma and that germ line deletion of the GSNOR gene in mice causes hepatocellular carcinoma through S-nitrosylation and proteasomal degradation of the key DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). We report here the generation of mice with targeted deletion of GSNOR in hepatocytes or in cells of the hematopoietic lineage. We found that during inflammatory responses induced by intraperitoneal injection of diethylnitrosamine (DEN) or lipopolysaccharide, the amount of liver AGT was not changed in mice with GSNOR deletion in hematopoietic cells but was almost completely depleted in mice with GSNOR deletion in hepatocytes. In livers of DEN-challenged mice, GSNOR deletion in hepatocytes but not hematopoietic cells resulted in an increase in phosphorylated histone H2AX, a well-established marker of DNA double-strand breaks. Hepatocyte deletion of GSNOR increased DEN-induced mortality, which was abolished in mice deficient in both GSNOR and inducible nitric oxide synthase. Thus, protection of AGT and resistance to nitrosamine-induced genotoxicity critically depends on GSNOR in hepatocytes. In addition, our findings suggest that nitrosative inactivation of AGT from GSNOR deficiency might sensitize cancerous cells to alkylating drugs in cancer treatment.
authors.affiliation: Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Yang
authors.forename: Chi-Hui
authors.initials: CH
authors.lastname: Tang
authors.forename: Limin
authors.initials: L
authors.lastname: Liu
mesh_terms: D000426:Alcohol Dehydrogenase; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D004052:Diethylnitrosamine / Q000633:toxicity*; D017353:Gene Deletion; D005980:Glutathione Reductase / Q000235:genetics*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D051379:Mice; D009153:Mutagens / Q000633:toxicity*; D015538:Nitrosation; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000037:antagonists & inhibitors*; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D009153:Mutagens; D004052:Diethylnitrosamine; C483598:Adh5 protein, mouse; D000426:Alcohol Dehydrogenase; D005980:Glutathione Reductase; D019853:O(6)-Methylguanine-DNA Methyltransferase